i jump start my 02 lancer but it shuts right off when i remove jumper cables.

What is your question?

i bought a used altanator 3 days ago cuz my car was nt speeding up right in the hwy on my way to gwinnett from acworth. but i jump start the car and it stays on as long as i keep jumper cables on. as soon as i remove them the car just shuts off. even if i start pressing the gas petal it shuts off. i dont know if its my battery or if it has to do with gas or electrical. all i know is when i remove jumper cables the lights on the dash get dim then it just wont cut on anymore after a few seconds. checked my fuel pump but is working fine. can someone please help me? i been stuck in gwinnett county for the last 3 days . going on my fourth.